Update values on other Tab

[ClSoft]

Hi all
I'm 100% new on Web and JavaScript stuff - I wanted that you know that 

If I have Panel,  on North part I have treeGrid and on South part 3 Tab's.
On onClickEvent (on treeGrid) I want to update some value on Tab 2 (on South part).

I found example on how to do that on same page, but how to update value on other page?
Thanks!